Multiple sensor resin delivery optimizing vacuum pump operation

ABSTRACT

Method and apparatus for pneumatically conveying granular resin material and controlling such conveyance includes a sensor associated with granular plastic resin material receiver with the sensing vacuum level thereat and a microprocessor adjusting vacuum pump speed based on vacuum level sensed at the receiver.

CROSS REFERENCE TO RELATED PATENTS AND PATENT APPLICATIONS

This patent application is a 35 USC 120 division of co-pending patentapplication U.S. Ser. No. 15/064,995, the priority of which is claimedand asserted as a matter of law under 35 USC 120 for this divisionalapplication. This patent application, through the co-pending '995application, claims the benefit of the priority under 35 USC 120 of U.S.provisional patent application Ser. No. 62/131,935 filed 12 Mar. 2015.

This patent application through the co-pending '995 application and 35USC 120 claims the benefit of the priority of U.S. patent applicationSer. No. 14/185,016 filed 20 Feb. 2014 in the name of Stephen B. Maguireand entitled “Air Flow Regulator,” published 20 Aug. 2015 as UnitedStated patent publication 2015/0232287 A1, now issued as U.S. Pat. No.9,371,198.

This patent application through the co-pending '995 application and 35USC 120 claims the benefit of the priority of U.S. patent applicationSer. No. 14/574,561 filed 18 Dec. 2014 in the name of Stephen B. Maguireand entitled “Resin Delivery System With Air Flow Regulator,” published20 Aug. 2015 as United States patent publication 2015/0231801 A1, nowissued as U.S. Pat. No. 9,604,793.

This patent application through the co-pending '995 application and 35USC 120 claims the benefit of the priority of U.S. patent applicationSer. No. 14/593,010 filed 9 Jan. 2015 in the name of Stephen B. Maguireand entitled “Air Flow Limiter with Closed/Open Sensing,” published 20Aug. 2015 as United States patent publication 2015/0232289 A1, nowissued as U.S. Pat. No. 9,550,635.

This patent application through the co-pending '995 application and 35USC 120 claims the benefit of the priority of U.S. patent applicationSer. No. 14/602,784 filed 22 Jan. 2015 in the name of Stephen B. Maguireand entitled “Method and Apparatus For Resin Delivery With AdjustableAir Flow Limiter,” published 20 Aug. 2015 as United States patentpublication 2015/0232290 A1, now issued as U.S. Pat. No. 9,550,636.

This patent application is still further a 35 USC 120continuation-in-part of U.S. patent application Ser. No. 14/804,404filed 21 Jul. 2015 in the name of Stephen B. Maguire and entitled“Vacuum Powered Resin Loading System Without Central Control,” published12 Nov. 2015 as United States patent publication 2015/0321806 A1, thepriority of which is claimed under 35 USC 120.

The disclosures of all the foregoing patents and published patentapplications are hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable—this invention was conceived and developed entirely usingprivate source funding; this patent application is being filed and paidfor entirely by private source funding.

BACKGROUND OF THE INVENTION

This invention relates to manufacture of plastic articles and moreparticularly relates to pneumatic conveyance and processing of plasticresin pellets prior to molding or extrusion of those pellets into afinished or semi-finished plastic product.

In this patent application, injection and compression molding pressesand extruders are collectively referred to as “process machines.”

The plastics industry is very diversified; there are thousands ofdifferent products, hundreds of materials, and dozens of processes, andall are very different from one another. The only thing all these sharein common is that the source material is some type of plastic.

Equipment sold to this industry is, therefore, very diversified indesign. Plastics factories have multiple process machines, sometimesseveral hundred in one location. Virtually all plastics fabricatingoperations require that each process machine, namely a molding press oran extruder, be supplied automatically with the required raw resinmaterial on a continuous basis. This resin may be supplied in largeboxes called “Gaylords”, in fiber drums, in 50 pound bags, or moretypically may be delivered by bulk truck or rail car, with the resinmaterial then being transferred in bulk into storage silos. In all casesthe resin material must be further distributed throughout the plant tothe process machines. For that reason a great deal of design and capitalexpense is devoted to the automatic distribution of the raw resinmaterial throughout the plant.

These resin distribution systems, more commonly referred to as “LoadingSystems”, must deal with many variables. One set of variables includesthe type, shape, size and consistency of the granular material.

Resin pellets, nominally about ⅛ inch in size, come in various shapes,with round, square, and cylindrical being the most common.

Flowing resin powder is also an option, and very fine but free flowingresin pellets and other granular materials may be conveyed as well.

The design variables to be considered for each customer include:

-   -   1. Type of resin being conveyed.    -   2. Size and consistency of the resin pellets.    -   3. Distances the resin pellets are to be conveyed.    -   4. Variability of these distances from shortest to longest.    -   5. Acceptable range for velocity of resin material travel        through the lines.    -   6. Throughput rate of resin required for each machine.    -   7. Total throughput rate of resin for the entire plant.    -   8. Excess capacity performance margin so a molding or extrusion        process is not interrupted by short term loading issues.    -   9. Loss of resin material from or at the supply so that only air        is being pulled, thereby reducing system vacuum levels and        reducing overall design throughput.    -   10. Loading sequence, or priority, when multiple receiver        stations call for material.    -   11. Detecting problems and alarm conditions.    -   12. Proper air to material ratio for resin conveying.    -   13. Detecting plugged lines due to poor resin flow or over        feeding of resin material.    -   14. Dust condition and filter requirements.    -   15. Reliability.    -   16. Serviceability.    -   17. Ease of use.    -   18. Cost    -   19. Vacuum pump type, namely positive displacement,        regenerative, and others.    -   20. Vacuum pump horsepower and rated CFM capacity as well as        vacuum levels.

In all of these areas, system designers look to find improved methodsand solutions whenever possible.

One of the most important considerations is to hold a correct velocityduring conveyance for the conveyed resin material. The type of resinmaterial dictates the target conveying speed. To maximize the resinmaterial transfer rate, a high conveying speed is preferred, and airspeed in any case must be sufficient to keep the resin pellets suspendedand moving in the air stream. But velocity must be limited so as not todamage the pellets. Hard brittle pellets can fracture and break whenconveyed, resulting in excessive dust.

Softer pellets can skid along the conduit walls, causing “angel hair” asa result of the plastic resin melting at the point of high speed contactwith the conduit wall; this leaves a thin film on the wall. Strings ofvery thin “angel hair” accumulate, effectively reducing diameter of theconduit and causing problems in the system.

Air speed and resin conveying velocity are directly related to pumpcapacity (rated in Cubic Feet per Minute, abbreviated as “CFM”) andhorsepower, as well as conveying line diameter. There is always acorrect velocity “range” for each type of resin material. It is a designchallenge to assure that the resin material is conveyed within thecorrect velocity range.

Conveying distances affect system design. Conveying over short distancesrequires a less powerful vacuum source then over longer distances.Systems are generally sized to produce the best compromise for materialvelocity between the shortest and longest conveying distance.

Required conveying rate usually dictates line size (conduit diameter),and this in turn dictates the CFM required to maintain correct velocityin a given diameter conduit. This means different conduit sizes in thesame system can be a problem if one vacuum pump is to draw air and resinthrough several different diameter conveying lines. Pumps have known CFMratings. Pulling air through a small conduit will result in highervelocity flow than pulling the same CFM through a larger conduit.

Excessive velocity can damage pellets.

The type of vacuum pump to be selected is important. Regenerativeblowers deliver wide ranging CFM depending on vacuum level. Positivedisplacement type pumps deliver high vacuum levels, and have a flatterCFM curve over their vacuum range. Regenerative blowers are quieter andgenerally cost less. Positive displacement blowers may require soundenclosures and tend to cost more, but are generally more reliable andmore forgiving as respecting dust in the air.

The simplest systems use a fixed speed motor to drive the vacuum pump,and a single size conveying line to serve all receivers regardless ofconveying distance, conveying rate requirement, or the material beingconveyed.

VFD (Variable Frequency Drive) motors allow vacuum pumps to operate atdifferent speeds, and therefore at different CFM rates, with the vacuumpump pulling different vacuum levels depending on preset informationabout each receiver being served.

The addition of a SCFM (Standard Cubic Feet per Minute) limiter in theair flow line allows oversized vacuum pumps to be used without risk ofconveying at excessive velocity. SCFM limiters restrict air flow to apreset SCFM. This maintains the desired SCFM air flow at the inlet,which is critical for proper conveying in a given size conveying line.

DESCRIPTION OF THE PRIOR ART

Current resin central loading systems concerned with conveying granularplastic resin pellets from a storage area for molding or extrusiontypically include a vacuum pump or pumps and multiple receivers.

In some systems, with many receivers, several small pumps are used.

It would be less expensive to use only one, or fewer, larger pumps.However, a larger pump may draw too much air with resulting damage tothe material being conveyed. While a larger pump could load severalreceivers at once, there is a risk that an “open” line, namely a linepulling only air, and no resin material, would cause the vacuum to droptoo much, and no resin would load. Also, when only one receiver isloading resin, air velocity might be too high, again with a risk ofdamaging the resin.

Nevertheless, in facilities that fabricate plastic products by moldingor extrusion, it is common to use such vacuum loading systems topneumatically convey pellets of thermoplastic resin, prior to molding orextrusion of those pellets into a finished or semi-finished product. Theplastic resin pellets are typically purchased in 50 pound bags, 200pound drums, or 1,000 pound containers commonly referred to as“Gaylords.”

A common approach for conveying plastic resin pellets from a storagelocation to a process machine, which approach is often used in largerfacilities, is to install a central vacuum pump or even several vacuumpumps, connected by common vacuum lines to multiple “receivers.”

Vacuum pumps connected to the vacuum lines draw vacuum, namely air atpressure slightly below atmospheric, as the vacuum pump sucks airthrough the “vacuum” line. The suction moves large quantities of airwhich carries thermoplastic resin pellets through the “vacuum” line.

An alternative is to use positive pressure produced by a blower or theexhaust from a vacuum pump. With such an approach, the positive pressureresults in a movement of substantial amounts of air which may be used tocarry the plastic resin pellets. However, the vacuum approach of drawingor sucking or pulling pellets through the system conduit(s) ispreferable to the positive pressure approach of pushing the resinpellets through the system conduit(s).

In practice, vacuum pumps are preferred and vacuum lines are desirablein part because power requirements to create the required vacuumnecessary to draw plastic resin pellets through the lines are lower thanthe power requirements if the plastic resin pellets are pushed throughthe lines by a blower or by the exhaust side of a vacuum pump. Whenvacuum is used, the static pressure within the line may be not much lessthan atmospheric. When positive pressure is used, the dynamic pressureof the air flowing through the line must be relatively high in order tomove an adequate quantity of plastic resin pellets.

As used herein, and in light of the foregoing explanation, the terms“vacuum pump” and “blower” are used interchangeably.

When one or more central vacuum pumps are connected to multiplereceivers, a receiver is typically located over each temporary storagehopper, in which the plastic resin pellets are temporarily stored beforebeing molded or extruded. A temporary storage hopper is typicallyassociated with each process machine.

In current practice, the receiver is connected by a control wire to acentral control system. The control system works by selectively openinga vacuum valve located in each receiver, allowing one or several vacuumpumps to work in sequence drawing “vacuum”, i.e. below atmosphericpressure air, to carry the pellets among and to multiple receivers asindividual ones of the receivers, positioned over individual hoppersassociated with individual process machines, require additional plasticresin pellets. The receiver for a given hopper-process machinecombination is actuated by opening the vacuum valve located in or nearthe receiver, causing the receiver to supply plastic resin pellets bygravity feed into the hopper from where the pellets may be fed furtherby gravity downwardly into the associated process machine.

Large, high capacity industrial vacuum pumps are reliable and are suitedto heavy duty industrial use. Large, high capacity vacuum pumps allowlong conveying distances for the plastic resin pellets. Currentlyavailable large capacity vacuum pumps permit plastic resin pellets to beconveyed over distances of 200 feet or more using vacuum drawn by thepump. Use of such high capacity vacuum pumps results in a big rush ofbelow atmospheric pressure air through the line, carrying the plasticresin pellets over a long distance. The vacuum pump speed is notmodulated; the vacuum pump is either “on” or “off.” As a result, whenthe pump is operating, “vacuum”, more accurately “air”, is drawn at afixed rate by the vacuum pump through the system.

Operators of plastic manufacturing facilities prefer to buy plasticresin pellets in bulk, in rail cars or tanker trucks. Bulk purchasesresult in cost savings. Plastic resin pellets delivered in bulk aretypically pumped into large silos for storage. In a large manufacturingfacility, the distance from a plastic resin pellet storage silo to aprocess machine may be several hundred feet, or more. Accordingly, whenplastic resin pellets are purchased in bulk, a central vacuum-poweredconveying system, powered by one or more large, high capacity industrialvacuum pumps, is a necessity.

Typically, large central plastic resin pellet conveying systems have oneor more vacuum pumps, each typically being from 5 to 20 horsepower.These central systems include central controls connected by wire to eachreceiver associated with each process machine in the facility. Typicallyeight, sixteen, thirty-two or sixty-four receivers, each associated witha process machine, may be connected to and served by the central plasticresin pellet vacuum conveying system. Of course, the higher the numberof receivers served by the system, the higher the cost. The centralcontrol is connected by wire to each receiver and is used to signal whena receiver is empty and therefore needs and should receive granularresin material. The central control, wired to each receiver, does notmeasure vacuum level at the receiver and is not in any way used tomoderate or modulate operation of the vacuum pump.

A factor to be considered in designing such a system is the speed of theplastic resin pellets as they flow through a conduit as the plasticresin pellets are carried by the moving air stream drawn by the vacuumpump. If air flow is too slow, the plastic resin pellets fall out of theair stream and lie on the bottom of the conduit, with resulting risk ofclogging the conduit. If air flow is too fast, the plastic resin pelletscan skid along the conduit surface. In such case, harder, more brittleplastic resin pellets may be damaged, resulting in dust within theconduit, which when drawn into the vacuum pump can damage the vacuumpump and render the system inoperative. Softer plastic resin pelletsheat up and can melt from friction when contacting the conduit interiorsurface. This results in “angel hair”—long, wispy-thin strands ofplastic film which eventually clog the conduit and cause the system toshut down.

For these reasons, pneumatic plastic resin pellet conveying systems mustbe designed to produce desired, reasonable conveying speeds for theplastic resin pellets.

Currently, conveying speed of the plastic resin pellets is most oftencontrolled by controlling air flow, measured in cubic feet per minute,and varying the desired and designed cubic feet per minute based onconduit diameter, with a larger diameter conduit requiring more cubicfeet per minute of air flow to maintain proper air flow speed throughthe conduit. Controlling air flow, measured in cubic feet per minute, isconventionally done by specifying the vacuum pump capacity; vacuum pumpspeed modulation is not within the state of the art.

Controlling cubic feet per minute of air flow is an indirect way ofcontrolling plastic resin pellet speed as the plastic resin pellets flowthrough a conduit of a given diameter. Typically, a 2 inch diameterconduit requires about 60 cubic feet per minute of air flow to conveytypical plastic resin pellets. A 2½ inch diameter conduit typicallyrequires about 100 cubic feet per minute of air flow to convey typicalplastic resin pellets. To achieve these desired air flow volume flowrates, a designer must carefully match the horsepower of a vacuum pump,which has a given cubic feet of air per minute rating, to a selectedsize conduit, taking into consideration the average distance the plasticresin pellets must be conveyed through the conduit from a storage siloto a receiver or loader (because resin conveyance systems are notdesigned for modulation of vacuum pump speed for the reason notedabove—vacuum pump speed modulation is not within the state of the art).If this results in selection of a 5 horsepower blower/vacuum pump, thena given facility may require several such blowers/vacuum pumps, witheach blower/vacuum pump supplying only a selected number of receivers.

A single plastic resin molding or extruding facility might theoreticallyrequire a 20 horsepower blower and the corresponding cubic feet perminute capability for conveyance provided by the single blower to meetthe total conveying requirements for plastic resin pellets throughoutthe facility. However, a single twenty horsepower blower would result infar too high a conveying speed for the plastic resin pellets through anyreasonable size conduit. As a result, the conveying system for theplastic resin pellets in a large facility is necessarily divided andpowered by three or four smaller blowers, resulting in three or fourdifferent, separate systems for conveyance of plastic resin pellets.Sometimes several blowers are connected to a single set of receivers,with one or more of the extra blowers turning “on” only when required tofurnish the required extra cubic feet per minute of air flow. This iscontrolled by a central station monitoring all receivers and allblowers, with the central station being programmed to maintain all ofthe hoppers associated with the process machines in a full condition,wherever those hoppers are located throughout the facility.

Even with careful planning and design, results achieved by suchpneumatic plastic resin pellet conveying systems are not consistent. Airflow speed and cubic feet per minute capacity of blowers often vary andare outside of selected design and specification values.

INCORPORATION BY REFERENCE

In addition to the patents and published patent applications listedabove under the heading “Cross Reference to Related Patents and PatentApplications,” the disclosure of U.S. Pat. No. 8,753,432 is alsoincorporated herein by reference.

SUMMARY OF THE INVENTION

The inventive technology offers controls and devices that can maximizeperformance for the variety of conditions that actually exist in aplant.

In one of its aspects, this invention provides apparatus forpneumatically conveying granular plastic resin material where theapparatus includes a resin supply, a vacuum pump having a suctionintake, and a plurality of receivers for temporarily storing resinmaterial until needed by an associated process machine. A conduitconveys granular resin material from the resin supply to the receiversin response to vacuum drawn through the conduit by the vacuum pump. Oneor more sensors associated with one or more of the receivers sensevacuum level at the receiver. A sensor at the vacuum pump suction intakesenses vacuum level thereat. The method further embraces adjustingvacuum pump speed based on vacuum levels sensed optimally and optionallyat the receivers and at the vacuum pump. Desirably, at least one sensoris associated with each receiver so that vacuum pump speed can beadjusted based on vacuum level sensed at all of the receivers, anddesirably at the vacuum pump as well, thereby providing optimumconditions for a pneumatic transport of the granular plastic resinmaterial from the supply to the receivers.

In still another one of its aspects, this invention provides a methodfor pneumatically conveying plastic resin material from a resin supplyusing a resin pump having a suction intake where the method includesproviding a plurality of receivers for temporarily storing resinmaterial until needed by an associated process machine. The methodfurther proceeds with providing a conduit for conveying granular resinmaterial from the resin supply to the receivers in response to vacuumdrawn through the conduit by a vacuum pump. The method yet furtherproceeds by periodically sensing vacuum level at each receiver, storingthe sensed vacuum levels, actuating the vacuum pump and adjusting vacuumpump speed based on the stored vacuum levels.

Desirably the sensed vacuum levels are sensed serially at the receivers.The method may further embrace adjusting the pump speed based onmultiple collections of serially sensed vacuum levels. The method mayyet further embrace periodically sensing vacuum level at the vacuumpump, which vacuum level may be sensed serially. The method then furtherembraces adjusting the pump speed based on multiple collections ofserially sensed vacuum levels including vacuum level at the vacuum pump.

In another one of its aspects, this invention provides a method forconveying granular plastic resin material from a supply thereof to atleast one receiver, for temporary storage of the granular plastic resinmaterial in the receiver until the material is needed by a processmachine associated with the receiver, where the method includespositioning a first conduit with an open end in the supply of granularplastic resin material. The method proceeds by drawing vacuum throughthe first conduit, thereby conveying granular plastic resin material outof the supply and along the conduit. The method then provides a receiverconnected to the conduit for receipt of granular resin material from theconduit. Next, a second conduit is provided, connecting the receiver toa source of the drawn vacuum, which draws vacuum through the firstconduit via the receiver. Next, the invention proceeds by providing atleast one vacuum sensor in the first conduit and regulates vacuumdrawing according to sensed vacuum level at the vacuum sensor.

In this aspect of the invention, the method may further provide a secondvacuum sensor in the second conduit and regulate vacuum draw accordingto vacuum levels sensed at the two vacuum sensors.

In this aspect of the invention, the method may yet further involveproviding a vacuum sensor at the receiver and regulating vacuum drawaccording to vacuum levels sensed at the three vacuum sensors, onesensor at the receiver, one sensor in the second conduit, and one sensorin the first conduit.

In this one of its aspects, the invention further provides a method forconveying granular plastic resin material from a supply thereof to atleast one receiver as noted in the three preceding paragraphs, where themethod further includes regulating vacuum draw according to an algorithmexecuted by a computing device based on input signals received from thevacuum sensors.

In still yet another one of its aspects, this invention provides amethod for conveying granular plastic resin material from a supplythereof to at least one receiver for temporary storage of granularplastic resin material in the receiver until the material is needed by aprocess machine associated with the receiver. In this aspect of theinvention, the method commences with positioning a first conduit with anopen end in the resin supply. The method proceeds by drawing vacuumthrough the first conduit, thereby conveying granular plastic resinmaterial out of the supply and along the conduit. The method yet furtherproceeds by providing a receiver connected with the conduit for receiptof granular resin material from the conduit. A second conduit isprovided connecting the receiver to the vacuum source providing thedrawn vacuum via the receiver to the first conduit. At least one vacuumsensor is provided on the first conduit. Vacuum levels are then recordedas provided by the sensor. Recorded vacuum levels are correlated withobserved conveyance of granular resin material from the supply to thereceiver, with the recording being done in a computing device,preferably a microprocessor, to create an executable algorithm foroptimized conveyance of the granular resin material. The algorithm isexecuted in the computing device to regulate the vacuum draw.

In this aspect of the invention, the computing device is desirably amicroprocessor. The method yet further includes the steps of recordingphysical parameter data including at least one of ambient temperature,atmospheric pressure, relative humidity, and available line voltage, andusing data reflecting at least one of those physical parameters increating the executable algorithm.

The foregoing outlines rather broadly features of the invention in orderthat the detailed description of the invention that follows may be bestunderstood. Additional features and advantages of the invention, asdescribed hereinafter, may form the subject of certain of the claims ofthe application. It will be appreciated by those skilled in the art thatthe concepts and specific embodiments disclosed herein may be readilyutilized as a basis for modifying or designing apparatus or othermethods for carrying out the goals and results attained by thisinvention. It should also be realized by those skilled in the art thatsuch equivalent implementations do not depart from the spirit and scopeof the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a resin delivery system inaccordance with aspects of the invention.

FIG. 2 is a schematic representation of an alternate embodiment of aresin delivery system in accordance with aspects of this invention.

In reference to the drawings, where reference numbers are identical tothose used in the description to designate like or similar elementsthroughout the various views, illustrative implementations of theinvention are described. The figures are schematic and therefore not toscale. In some instances the drawings have been exaggerated and/orsimplified for illustrative purposes. One of skill in the art willappreciate the many possible applications and variations of theinvention that are possible based on the following description of thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

In this application, unless otherwise apparent from the context, it isto be understood that the use of the term “vacuum” means “air atslightly below atmospheric pressure.” The vacuum (meaning air slightlybelow atmospheric pressure) provides a suction effect that is used todraw granular plastic resin material out of a supply and to convey thatgranular plastic resin material through various conduits to receiverswhere the granular resin material can be temporarily stored before beingmolded or extruded. Hence, in this application it is useful for thereader mentally to equate the term “vacuum” with the term “suction”.

Referring to the drawings in general and to FIG. 1 in particular,apparatus for conveying granular plastic resin material from the supplyto receivers that retain and dispense the resin material when needed bya process machine is illustrated in FIG. 1. The apparatus, which isdesignated generally 88 in FIG. 1, preferably includes a vacuum pumpdesignated generally 92 and shown schematically in FIG. 1. Vacuum pump92 preferably includes a vacuum pump suction head 93 also shownschematically in FIG. 1. Connected to the vacuum pump suction head 93may be an optional airflow limiter 30 shown only in schematic form inFIG. 1. Optional airflow limiter 30 receives vacuum drawn by vacuum pump92 through vacuum drawing conduit 100.

The optional air flow limiter 30 is preferably one of the types of airflow limiters disclosed in the United States patents listed above underthe heading “Cross Reference to Related Patents and PatentApplications.” All of these air flow limiters, which are the preferabletype of flow limiters for use in the instant invention, must be verticalor essentially vertical in order to function properly. In the drawings,all of flow limiters 30 have been illustrated in a vertical orientation.However, it is to be understood that other kinds and styles of flowlimiters may be used in the course of practice of the invention.

Vacuum drawing conduit 100 is connected to a plurality of receivers 16,each of which receives, retains and dispenses, as needed, granularplastic resin material to a process machine, such as a gravimetricblender, or an extruder, or a molding press as located preferably belowa receiver 16. The process machines are not illustrated in FIG. 1 toenhance the clarity of the drawing.

Further illustrated in FIG. 1 is a hopper 18 for storage of granularplastic resin material therein and a resin conveying conduit 98, whichserves to draw resin from hopper 18 and to deliver the resin throughresin conveying conduit 98 to the respective receivers 16 as vacuum isdrawn by the vacuum pump 92, with vacuum propagating through optionalair flow limiter 30, vacuum drawing conduit 100, the various receivers16, and resin conveying conduit 98, to hopper 18. Receivers 16 arepreferably of the type disclosed and claimed in U.S. Pat. No. 8,753,432.

Still referring to FIG. 1, a plurality of vacuum sensors areillustrated. Vacuum sensors 130 are provided associated with eachreceiver and located upstream of each receiver to sense the vacuum inresin conveying conduit 98 as that resin conveying conduit conveys resininto a receiver 16. Vacuum sensors 132 are positioned downstream of eachreceiver to sense vacuum at a position proximate to each receiver invacuum drawing conduit 100. A vacuum sensor 134 is provided to sense thevacuum being drawn by vacuum pump 92 at a position proximate to vacuumpump suction head 93.

While the resin conveying system 88 illustrated in FIG. 1 has beendepicted with vacuum sensors 130 upstream of each receiver, vacuumsensors 132 downstream of each receiver, and a vacuum sensor 134 atvacuum pump 92, in some implementations of the invention, only vacuumsensors upstream of receiver 16, or vacuum sensors downstream ofreceiver 16 may be used. Moreover, it is within the scope of theinvention to provide a vacuum sensor within one or more of the receivers16 as indicated by vacuum sensors 136 illustrated in FIG. 1. It isfurther within the scope of the invention to provide only a few vacuumsensors 130 or 132 or 136, located at strategic positions upstream of areceiver, downstream of a selected receiver, or within a selectedreceiver. Optionally but desirably a vacuum sensor 138 may also beprovided at resin supply 18 to sense the level of vacuum being drawn byvacuum pump 92 through resin conveying conduit 98 proximate resin supply18.

However many vacuum sensors are used, all of these vacuum sensorsprovide data, preferably wirelessly, to a controller illustrated onlyschematically in the drawings, which is desirably in the form of amicroprocessor 200. Microprocessor 200 collects data from one or more ofthe sensors 130,132, 134, 136, 138 preferably sequentially through thesensors in that only a single receiver 16 is usually active at a giventime, so desirably the vacuum data relevant to a given receiver 16 iscollected only when that receiver 16 is active. (Other data collectionschemes, such as serial or random, and algorithmic protocols based onvarious physical and other parameters such as relative humidity, ambienttemperature, atmospheric pressure, available line voltage for the vacuumpump, and the like, are also within the scope of this invention.) Thissensed vacuum data and the other physical parameter data are preferablystored and used based preferably on an experientially developedalgorithm (developed using such data) which is executed bymicroprocessor 200 to optimally modulate operation of vacuum pump 92.This data may desirably be correlated with time of day, the type ofresin being conveyed, the temperature within the facility, and otherphysical parameters so as to provide a mathematical algorithm that maybe used to optimize the speed of vacuum pump 92.

Alternatively to wireless communication of the vacuum sensors 130through 138 with microprocessor 200, wiring can, of course, be used.

FIG. 2 shows an alternate embodiment of the resin conveying system ofthe invention where this alternate embodiment of the conveying systemhas been designated 88A. FIG. 2, as in FIG. 1, depicts a vacuum pump 92shown in schematic form having a vacuum pump suction head 93 alsodepicted in schematic form. In the alternate embodiment of the inventionillustrated in FIG. 2, vacuum drawing conduit 100 leads directly intoand communicates with vacuum pump suction head 93. In the embodimentillustrated in FIG. 2, an optional air flow limiter 30 is shown as beingprovided for each receiver 16, with the air flow limiter 30 for arespective receiver 16 being located in a portion of a connectionconduit 102 that connects a respective receiver 16 to vacuum drawingconduit 100. In FIG. 2, each air flow limiter 30 is depicted in avertical orientation, just as is airflow limiter 30 depicted in avertical orientation in FIG. 1. Each receiver 16 is connected byconnection conduit 102 to vacuum drawing conduit 100 with optional airflow limiter 30 forming a portion of connection conduit 102. The airflow limiters 30 illustrated in FIG. 2 are desirably one of the type ofair flow limiters disclosed above with reference to FIG. 1.

In FIG. 2, as in FIG. 1, a first conduit 98 serves to convey granularplastic resin from hopper 18 to the respective receivers in response tovacuum drawn by vacuum pump 92 as that vacuum propagates from vacuumpump 92 through second conduit 100, connection conduits 102, receivers16, and resin conveying conduit 98 to hopper 18. The resin conveyingsystem shown in FIG. 2 is similar to that shown in FIG. 1 in that itincludes a variety of vacuum sensors with vacuum sensors 130 beinglocated upstream of associated receivers 16; vacuum sensors 132 beinglocated downstream of respective receivers 16; a vacuum sensor 134 beingprovided at vacuum pump 92; a plurality of vacuum sensors 136 beingprovided within receivers 16; and a vacuum sensor 138 desirably beingprovided at the resin supply to measure the vacuum drawn within resinsupply conduit 98 proximate resin supply 18. As with the resin conveyingsystem illustrated in FIG. 1, the vacuum sensors illustrated in FIG. 2are desirably connected to a microprocessor 200, or other, more powerfulcomputing device, wirelessly. Alternatively, the vacuum sensors can beconnected by wires to microprocessor 200 or some other computing device,if necessary. The same approach to optimizing speed and modulation ofthe vacuum pump 92 as described above with respect to FIG. 1 isapplicable to the resin conveying system illustrated in FIG. 2.

During operation of the resin conveying systems shown schematically inFIGS. 1 and 2, upon actuation of vacuum pump 92, a vacuum is drawn atvacuum pump suction head 93. This vacuum, as it propagates to hopper 18,serves to draw resin out of hopper 18 and into respective receivers 16.In the embodiment illustrated in FIG. 2, optional individual air flowlimiters 30 limit the suction or vacuum drawn by vacuum pump 92 througha given associated receiver 16. In the embodiment illustrated in FIG. 1,an optional single air flow limiter 30 limits vacuum drawn through allof receivers 16 forming a portion of the granular resin conveying systemillustrated in FIG. 1.

Although schematic implementations of present invention and at leastsome of its advantages have been described in detail hereinabove, itshould be understood that various changes, substitutions and alterationsmay be made to the apparatus and methods disclosed herein withoutdeparting from the spirit and scope of the invention as defined by theappended claims. Moreover, the scope of this patent application is notintended to be limited to the particular implementations of apparatusand methods described in the specification, nor to any methods that maybe described or inferentially understood by those skilled in the art tobe present as described in this specification.

As one of skill in the art will readily appreciate from the disclosureof the invention as set forth hereinabove, apparatus, methods, and stepspresently existing or later developed, which perform substantially thesame function or achieve substantially the same result as thecorresponding embodiments described and disclosed hereinabove, may beutilized according to the description of the invention and the claimsappended hereto. Accordingly, the appended claims are intended toinclude within their scope such apparatus, methods, and processes thatprovide the same result or which are, as a matter of law, embraced bythe doctrine of the equivalents respecting the claims of thisapplication.

As respecting the claims appended hereto, the term “comprising” means“including but not limited to”, whereas the term “consisting of” means“having only and no more”, and the term “consisting essentially of”means “having only and no more except for minor additions which would beknown to one of skill in the art as possibly needed for operation of theinvention.”

The following is claimed:
 1. A method for a pneumatically conveyingplastic resin material from a resin supply using a vacuum pump having asuction intake, comprising: a) providing a plurality of receivers fortemporarily storing resin material until needed by an associated processmachine; b) providing a conduit for conveying granular resin materialfrom the resin supply to the receivers in response to vacuum drawnthrough the conduit by the vacuum pump; c) periodically and seriallysensing vacuum level at at least some of the receivers; d) storing thesensed vacuum levels; e) actuating the vacuum pump; f) adjusting vacuumpump speed based on the stored vacuum levels.
 2. The method of claim 1further comprising adjusting pump speed based on multiple collections ofserially sensed vacuum levels.
 3. The method of claim 1 furthercomprising periodically sensing vacuum level at the vacuum pump.
 4. Themethod of claim 3 further comprising sensing vacuum level serially. 5.The method of claim 4 further comprising adjusting pump speed based onmultiple collections of serially sensed vacuum levels.
 6. A method forconveying granular plastic resin material from a supply thereof to atleast one receiver, for temporary storage of the granular plastic resinmaterial in the receiver until the material is needed by a processmachine associated with the receiver, comprising: a) positioning a firstconduit with an open end in the supply; b) drawing vacuum through thefirst conduit, thereby conveying granular plastic resin material out ofthe supply and along the conduit; c) providing a receiver connected withthe conduit for receipt of granular resin material from the conduit; d)providing a second conduit connecting the receiver to a vacuum sourceproviding the drawn vacuum via the receiver to the first conduit e)providing at least one vacuum sensor on the first conduit; f) regulatingoperation of the vacuum source according to sensed vacuum level at thevacuum sensor.
 7. The method of claim 6 further comprising: a) providinga vacuum sensor on the second conduit; and b) regulating operation ofthe vacuum source according to vacuum levels sensed at the vacuumsensors.
 8. The method of claim 7 further comprising: a) providing avacuum sensor at the receiver; and b) regulating vacuum draw by thevacuum source according to vacuum levels sensed at the vacuum sensors.9. The method of claim 7 further comprising: a) providing a computingdevice; b) regulating vacuum drawing according to an algorithm executedby the computing device based on input signals received from the vacuumsensors.